From dfa4cb7ade73e135e689270399f0e2b2a143447d Mon Sep 17 00:00:00 2001
From: clippered <clarke_overkill@yahoo.com>
Date: Wed, 18 Oct 2017 07:04:35 +1100
Subject: [PATCH] Fix #2123 : check that the source and destination are
 different for manual memcpy

---
 clippy_lints/src/loops.rs | 9 ++++++++-
 tests/ui/for_loop.rs      | 8 ++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/clippy_lints/src/loops.rs b/clippy_lints/src/loops.rs
index 97925b0bd0c..e647ff44772 100644
--- a/clippy_lints/src/loops.rs
+++ b/clippy_lints/src/loops.rs
@@ -749,7 +749,14 @@ fn get_indexed_assignments<'a, 'tcx>(
     ) -> Option<(FixedOffsetVar, FixedOffsetVar)> {
         if let Expr_::ExprAssign(ref lhs, ref rhs) = e.node {
             match (get_fixed_offset_var(cx, lhs, var), fetch_cloned_fixed_offset_var(cx, rhs, var)) {
-                (Some(offset_left), Some(offset_right)) => Some((offset_left, offset_right)),
+                (Some(offset_left), Some(offset_right)) => {
+                    // Source and destination must be different
+                    if offset_left.var_name != offset_right.var_name {
+                        Some((offset_left, offset_right))
+                    } else {
+                        None
+                    }
+                },
                 _ => None,
             }
         } else {
diff --git a/tests/ui/for_loop.rs b/tests/ui/for_loop.rs
index 083e6f9a6e5..03630f87108 100644
--- a/tests/ui/for_loop.rs
+++ b/tests/ui/for_loop.rs
@@ -548,3 +548,11 @@ pub fn manual_clone(src: &[String], dst: &mut [String]) {
         dst[i] = src[i].clone();
     }
 }
+
+#[warn(needless_range_loop)]
+pub fn manual_copy_same_destination(dst: &mut [i32], d: usize, s: usize) {
+    // Same source and destination - don't trigger lint
+    for i in 0..dst.len() {
+        dst[d + i] = dst[s + i];
+    }
+}